(A) FIELD OF THE INVENTION
The present invention relates generally to cylinder locks and associated keys. More particularly, the present invention is directed to pin tumbler-type cylinder locks and associated keys which exhibit improved pick-resistance and wear-resistant characteristics for both the lock and the key. Accordingly, the general objects of the present invention are to provide novel and improved devices of such character.
(B) DESCRIPTION OF THE PRIOR ART
Cylinder locks have proved immensely popular due to their versatility, ease of installation, modest cost and the relatively high degree of security provided by such locks. While numerous techniques have been advanced for enhancing the pick-resistance and the overall security provided by cylinder lock systems, conventional cylinder locks and keys are frequently subject to accelerated wear which can ultimately jeopardize the integrity and/or operability of the cylinder lock systems. Such excessive wear results not only from intense usage, but also frequently results from employing the inserted key and cooperating lock as a knob or handle for forcing the door open. By using the key/lock as a doorknob or fulcrum point, damaging stresses can be exerted on components of the lock mechanism and portions of the key so as to greatly accelerate the wear of the key and the lock.
U.S. Pat. No. 4,440,010 entitled "Lock and Key Device" discloses a locking system employing a key with a rib which extends from an upper portion of the key which is adjacent the bow. The rib is insertable into the keyway and cooperates with an inner face portion of the lock. Upon rotation the rib prevents the key from being removed from the lock as long as the key has not been rotated a complete revolution. The key rib also cooperates with portions of the lock so that the lock may be operated a considerable number of times without jeopardizing the precise positioning of the key in relation to the fittings of the locking mechanism.
U.S. Pat. No. 1,832,498 entitled "Tumbler Lock and Key Therefor" discloses a key which has a projecting pin at the shank of the key near the head. The pin is receivable in the keyway. The keyway is configured so that the key can only be inserted into the keyway in a given angular position, and the key must be rotated a full 360.degree. before withdrawal from the lock is permitted. The pin thus functions to retain the inserted key in the lock cylinder upon rotation of the key.
U.S. Pat. No. 3,961,506 entitled "Locks" discloses a lock and key assembly wherein the key has adjustable formations which project from one edge of the key blade. The lock has adjustable tumblers which cooperate with the formations on the key blade so as to afford a variable combination lock and key assembly. The adjustable formations on the key are disclosed as grub-screws which are threaded into transversely spaced threaded bores along one edge of the key blade. These screws may be caused to project various distances from the edge of the key blade to form the lock engaging formations for unlocking the lock.
The above-discussed examples of the prior art do not afford the requisite degree of security while simultaneously affording protection against wear induced damage to the key and/or lock.